Rail interface systems (“RIS”), also commonly referred to as rail accessory systems, is a generic term for a system for attaching weapon accessories to small firearms such as pistols, rifles and light machine guns. Common weapon accessories include tactical lights, laser aiming modules, forward hand grips, weapon sights and optics, and bipods. A variety of rail interface systems have been developed for military and civilian application, including Picatinny (MIL-STD-1913), KeyMod and M-Lok®. These rail interface systems are well known in the firearms industry and most weapon accessories are compatible with one or more rail interface system.
The KeyMod RIS was developed by VLTOR Weapon Systems of Tucson, Ariz., and released through Noveske Rifleworks of Grants Pass, Oreg., before being published in the public domain for adoption by the entire firearms accessory industry. The KeyMod RIS consists of a series of “key hole” shaped rail openings formed in the handguard or other weapon component and a complimentary nut. The KeyMod slot is distinctive with a larger diameter through-hole combined with a narrow slot. The KeyMod nut is stepped and the larger diameter end is chamfered to mate against chamfer edges on the backside of the KeyMod slot.
The M-LOK® RIS was developed by Magpul Industries, Corp. of Austin, Tex. and protected by several patents including U.S. Pat. Nos. 8,925,236; 9,239,209; 9,239,210; 9,429,388; and 9523,554. M-LOK® is a registered trademark of Magpul Industries, Corp. The M-LOK® RIS consists of a series of elongated rail openings (“slots”) formed in the handguard, rail or other weapon component, and a specialized T-slot nut capable of only 90-degree rotation. The “quarter-turn” T-slot nuts have a “cammed” surface that allow the “T” section to engage the backside of the handguard or rail when the fastener bolts draw down on the nuts securing the attachment of the accessory. The cammed surface also allows the “T” section to disengage the backside of the handguard or rail when fasteners are loosened.
KeyMod and M-Lok are popular rail interface systems that aim to supersede the Picatinny military standard rail interface system (MIL-STD-1913). Both KeyMod and M-Lok® rail interface systems eliminate the need for weapon components, particularly handguards to be fully outfitted with “Picatinny” style rails. Both KeyMod and M-Lok® RIS enable the user to have a slimmer, lighter, smoother and better fenestrated handguard/fore-end with accessories mounted only where needed, whereas a Picatinny handguard typically will have rail slots along its whole length resulting in a heavier and bulkier handguard with sharp edges and poorer barrel ventilation. However, both KeyMod and M-Lok® RIS require the use of separate specialized fasteners.